Hydrogen cyanide has been produced by decomposition of formaldehyde, ammoxidation of methane, and so forth. In recent years, the major portion of hydrogen cyanide commercially used has been supplied as a by-product obtained in the production of acrylonitrile by ammoxidation of propylene. However, with substantial improvements of catalysts for the production of acrylonitrile by ammoxidation of propylene, the amount of hydrogen cyanide by-produced has been decreased, and it has sometimes become difficult to ensure the supply of an adequate amount of hydrogen cyanide for the production of methacrylate by an acetone cyanhydrin process.
Transportation of hydrogen cyanide is difficult and dangerous because of its toxicity. It is, therefore, recommendable that hydrogen cyanide is used in a process where it is consumed immediately after it is produced.
The present invention is intended to provide a process which can be advantageously employed, for example, in those cases that:
(1) The change of catalyst and so forth in the existing equipment of production of acrylonitrile makes it difficult to ensure the amount of hydrogen cyanide to be supplied to the attached acetone cyanhydrin equipment; PA1 (2) The equipment of production of methacrylate is planned to construct independently from the acrylonitrile production equipment; and PA1 (3) It is planned to produce hydrogen cyanide which is to be fed to equipments of production of various hydrogen cyanide derivatives. PA1 Me is at least one element selected from the group consisting of V and W; PA1 Q is at least one element selected from the group consisting of Mg, Zn, La, Ce, Al, Cr, Mn, Co, Ni, Bi, U, and Sn; and PA1 a, b, c, d, e, f, g, h and i each represents the atomic ratio of the elements in the formula for which they are subscripts,
In recent years, the use of methanol as a fuel has been studied. When methanol is available more inexpensively, the process of the invention is particularly advantageous.
Hydrogen cyanide produced by the process of the invention contains reduced amounts of by-products and impurities compared with the one produced by ammoxidation of hydrocarbons such as propylene, isobutene, toluene, and xylene. In some case, therefore, it can be used as such without any special purification. In accordance with the process of the invention, in addition to hydrogen cyanide as a main product, only small amounts of carbon monoxide and carbon dioxide gas are produced.
The process of the invention has advantages over the conventionally widely used process of ammoxidation of methane in that the conversion of the feed is high, the catalyst is inexpensive, the reaction temperature is low, the disposal of waste gas is easy because nitrogen oxides are not almost produced, and in that the construction cost can be saved.
Various techniques are known for the production of hydrogen cyanide from methanol, including a method wherein a vanadium/tin oxide catalyst is used (Russian Pat. No. 106,226) a method wherein a tin/antimony oxide catalyst is used (British Pat. No. 913,836), a method in which a molybdenum oxide catalyst is used (British Pat. No. 718,112 and U.S. Pat. No. 2,746,843), a method in which a catalyst comprising molybdenum oxide and other various elements is used (U.S. Pat. No. 3,911,089), and a method in which an oxide catalyst comprising antimony, and iron, cobalt, nickel, manganese, zinc, uranium, or the like is used (Japanese Patent Publication No. 39839/79).
These methods, however, suffer from various disadvantages in the industrial practice thereof. For example, in the case of catalysts containing large amounts of vanadium, molybdenum, and the like, (1) since the simple combustion of ammonia occurs, decreasing the unit of ammonia, it is inevitably necessary to introduce steam for the prevention of combustion of ammonia, and (2) since the sublimation of the molybdenum component occurs during use, decreasing not only the activity of the catalyst, but also its strength, it is difficult to use the catalyst over a long period of time. On the other hand, catalysts composed mainly of antimony are preferred in that they cause almost no combustion of ammonia, and the reduction in activity and strength of the catalyst due to the dissipation of antimony does not occur. These catalysts, however, have disadvantages in that they are subject to changes with a lapse of time during use, and their strength is insufficient depending on the composition thereof.